BEST: It's close between TTYD and SPM, both of which had very interesting characters. SPM loses some points for lack of variety, then gains some back for the Flipside/Flopside residents, and then loses some more for not executing the Flip/Flop stuff very well, and for just being so annoying to navigate.
So, 59% TTYD, 41% SPM.
WORST: SM64. Being an early N64 game, everything looks creepy and soulless, but the place where it hurt SM64 the most was the hub (which would have been rather boring anyway, really).